If I could have only one, it would probably be my 442. There are other's I like way better, shoot way better, make a lot more sense when ticking off reasons... but realistically... that 442 sits in a convenient but safe place, in a nylon clip-on holster loaded with 135gr GDHP's, and inevitably gets grabbed on the way out the door when I think:
"I'll be gone 10 minutes tops to get some milk. I don't need to carry anything and besides I'm in a hurry. I don't want to hassle with changing my belt, threading a holster on, chambering a round, etc... I just want to be done running around for the day and watch some TV."
That 442 is probably more likely to be there to save my bacon some day than the 4" 19 I rarely carry (but would if such and such and this and that were called for).
442 for me. Had I bought a 642, or 638 that particular day, same difference to me.